221. Which of the following compounds is metallic and ferromagnetic?
A
$$V{O_2}$$
B
$$Mn{O_2}$$
C
$$Ti{O_2}$$
D
$$Cr{O_2}$$
Answer :
$$Cr{O_2}$$
222. Which of the following compounds is used as the starting material for the preparation of potassium dichromate?
A
$${K_2}S{O_4} \cdot C{r_2}{\left( {S{O_4}} \right)_3} \cdot 24{H_2}O$$ (Chrome alum)
B
$$PbCr{O_4}$$ (Chromite yellow)
C
$$FeC{r_2}{O_4}$$ (Chromite)
D
$$PbCr{O_4} \cdot PbO$$ (Chrome red)
Answer :
$$FeC{r_2}{O_4}$$ (Chromite)
223. When $$Mn{O_2}$$ is fused with $$KOH,$$ a coloured compound is formed, the product and its colour is:
A
$${K_2}Mn{O_4},\,{\text{purple}}\,{\text{green}}$$
B
$$KMn{O_4},\,\,{\text{purple}}$$
C
$$M{n_2}{O_3},\,\,{\text{brown}}$$
D
$$M{n_3}{O_4},\,{\text{black}}$$
Answer :
$${K_2}Mn{O_4},\,{\text{purple}}\,{\text{green}}$$
224. Which of the following is not correctly matched with the given example?
A
An element of first transition series which has highest second ionisation enthalpy - $$Cu.$$
B
An element of first transition series with highest third ionisation enthalpy - $$Zn.$$
C
An element of first transition series with lowest enthalpy of atomisation - $$Zn.$$
D
Last element of third transition series - $$Cd.$$
Answer :
Last element of third transition series - $$Cd.$$
225.
The aqueous solution containing which one of the following ions will be colourless?
$$\left( {{\text{At}}{\text{. no}}{\text{.}}\,Sc = 21,Fe = 26,} \right.$$ $$\left. {Ti = 22,Mn = 25} \right)$$
A
$$S{c^{3 + }}$$
B
$$F{e^{2 + }}$$
C
$$T{i^{3 + }}$$
D
$$M{n^{2 + }}$$
Answer :
$$S{c^{3 + }}$$
226. Which of the following oxidation state is common for all lanthanoids?
A
+ 2
B
+ 3
C
+ 4
D
+ 5
Answer :
+ 3
227. Among the lanthanides, the one obtained by synthetic method is
A
$$Lu$$
B
$$Pm$$
C
$$Pr $$
D
$$Gd$$
Answer :
$$Pm$$
228.
Which one of the following forms a colourless solution in aqueous medium?
$$\left( {{\text{At}}{\text{. no}}{\text{.}}\,\,Sc = 21,Ti = 22,} \right.$$ $$\left. {V = 23,Cr = 24} \right)$$
A
$${V^{3 + }}$$
B
$$C{r^{3 + }}$$
C
$$T{i^{3 + }}$$
D
$$S{c^{3 + }}$$
Answer :
$$S{c^{3 + }}$$
229. Which of the following catalysts is not correctly matched with the reaction?
A
Vanadium $$(V)$$ oxide in contact process for oxidation of $$S{O_2}$$ to $$S{O_3}.$$
B
Finely divided iron in Haber's process in conversion of $${N_2}$$ and $${H_2}$$ to $$N{H_3}.$$
C
$$PtC{l_2}$$ catalyses the oxidation of ethyne to ethanal in the Wacker process.
D
$$Ni$$ in presence of hydrogen for conversion of vegetable oil to ghee.
Answer :
$$PtC{l_2}$$ catalyses the oxidation of ethyne to ethanal in the Wacker process.
230. Cuprous ion is colourless while cupric ion is coloured because
A
both have half filled $$p$$ - and $$d$$ - orbitals.
B
cuprous ion has incomplete $$d$$ - orbital and cupric ion has a complete $$d$$ - orbital.
C
both have unpaired electrons in the $$d$$ - orbitals.
D
cuprous ion has complete $$d$$ - orbital and cupric ion has an incomplete $$d$$ - orbital.
Answer :
cuprous ion has complete $$d$$ - orbital and cupric ion has an incomplete $$d$$ - orbital.